1. Field of the Invention
The present invention relates to a pulsed iodine laser apparatus.
2. Description of Related Art
Concerning an iodine laser which emits 1.315 μm radiation from an excited iodine atom I(2P3/2), a Chemical Oxygen-Iodine Laser is called a COIL. The COIL is well known to be able to operate at a high power CW (continuous wave) mode. In order to operate the COIL, a singlet oxygen molecule (O2(1Δg)) is generated from the chemical reaction of chlorine gas with a BHP solution. The BHP solution is a mixed solution of hydrogen peroxide solution (H2O2) and potassium hydroxide (KOH) or sodium hydroxide (NaOH). The O2(1Δg) is sometimes called singlet oxygen. By mixing the generated O2(1Δg) with iodine molecules, iodine molecules are dissociated into iodine atoms. Further, the excited iodine atom (I(2P3/2)) is produced by the energy transfer of O2(1Δg) to a basic iodine atom (I(2P1/2)). Thus, a COIL runs the laser operation. Stephen C. Hurlick, et al., “COIL technology development at Boeing,” Proceedings of SPIE Vol. 4631, 101-115 (2002), Masamori Endo, “History of COIL development in Japan: 1982-2002,” Proceedings of SPIE Vol. 4631, 116-127 (2002), Edward A. Duff and Keith A. Truesdell, “Chemical oxygen iodine laser (COIL) technology and development,” Proceedings of SPIE Vol. 5414, 52-68 (2004) and Jarmila Kodymova, “COIL-Chemical Oxygen Iodine Laser: advances in development and applications,” Proceedings of SPIE Vol. 5958, 595818 (2005) explain about the COIL.
Most COILs operate in a CW (Continuous Wave) mode. While there is another type of iodine laser having the same oscillation wavelength as that of the COIL, this laser uses alkyl iodine such as CF3I, C2F5I, n-C3F7I, or i-C3F7I. Extensive research on this type of iodine laser has been conducted since in the 1960s. This alkyl iodine is irradiated with Ultraviolet pulsed radiation from a Xe flashlamp. By doing so, iodine molecules can be easily dissociated into iodine atoms. Since the iodine atoms are in an excited state, laser oscillation is possible. This type of iodine laser is called a flashlamp-excited iodine laser, or a photo-dissociated iodine laser. A flashlamp-excited iodine laser is known to be able to produce a giant pulse. Therefore, large laser systems have been developed for the purpose of realizing inertial confinement fusion (ICF). Klaus J. Witte, Ernst Fill, Gunter Brederlow, Horst Baumhacker, and R. Volk, “Advanced Iodine Laser Concepts,” IEEE Journal of Quantum Electronics, Vol. QE-17, 1809-1816 (1981) explains about this.
However, in order to make the scale of the flashlamp-pumped iodine laser large, many large flashlamps are necessary. Furthermore, a large pulsed-power electric supply is necessary. Accordingly, the laser apparatus becomes complicated and thus upsizing of the apparatus become a problem. Therefore, a pulsed iodine laser based on the COIL, whose scale can be made larger more easily than that of the flashlamp-pumped iodine laser, has been developed. M. Endo, K. Shiroki, and T. Uchiyama explain about this in “Chemically pumped atomic iodine pulse laser,” Appl. Phys. Lett. Vol. 59, 891-892 (1991) explains. Also, in order to laser oscillation efficiently, a hybrid system has been investigated. The hybrid system uses a mixture of alkyl iodine and a singlet oxygen, and flashlamps. N. G. Basov, N. P. Vagin, P. G. Kryukov, D. Kh. Nurligareev, V. S. Pazyuk, and N. N. Yuryshev, “Molecules of CH3I and n-C3F7I as iodine atom donors in a pulsed chemical oxygen-iodine laser,” Soviet Journal of Quantum Electronics, Vol. 14, 1275-1276 (1984), N. N. Yuryshev, “Pulsed COIL review,” Proceedings of SPIE Vol. 1980, 181-185 (1992), Nikolai N. Yuryshev, Nikolai P. Vagin, “Pulsed Mode of COIL,” Proceedings of SPIE Vol. 4760, 515-525 (2002), Kenji Suzuki, Kozo Minoshima, Daichi Sugimoto, Kazuyoku Tei, Masamori Endo, Taro Uchiyama, Kenzo Nanri, Shuzaburo Takeda, and Tomoo Fujioka, “High pressure pulsed COIL assisted with an instantaneous production of atomic iodine,” Proceedings of SPIE Vol. 4184, 124-127 (2001) and Masamori Endo, Kozo Minoshima, Koichi Murata, Oleg Vyskubenko, Kenzo Nanri, Shuzaburo Takeda, and Tomoo Fujioka, “High pressure pulsed COIL assisted with an instantaneous production of atomic iodine II,” Proc. SPIE 5120, 397-404 (2003) explain about this.
Since the purpose of these conventional pulsed iodine lasers is to realize ICF, the pulse width is in the picoseconds order, and around 10 ns at the longest. Although an amplifier is necessary to increase the output energy, single-pass amplification could not extract the output energy efficiently. Therefore, multi-pass amplification has been investigated, in which an input beam is propagated in the same amplifier many times. Zhuang Qi, Feng Hao, Wang Chengdong, Sha Guohe, Zhang Cunhao, “Model for amplifier of pulsed chemical oxygen-iodine laser,” Proceedings of SPIE Vol. 1980, 198-201 (1992), Zhuang Qi, Feng Hao, Wang Chengdong, Sha Guohe, Zhang Cunhao, “Model for amplifier of pulsed chemical oxygen-iodine laser,” Proceedings of SPIE Vol. 1810, 501-504 (1992) M. Endo, K. Kodama, Y. Handa, and T. Uchiyama, “Theoretical study of a large scale chemically pumped pulsed iodine laser amplifier,” Proceedings of SPIE Vol. 1810, 532-535 (1992) explain about the multi-pass amplification for the iodine laser amplifier.